How does C.S. Forester use imagery in Hornblower During the Crisis?

In the section titled, Hornblower's Tempatation, Hornblower reads the letter from McCool and finds that it contains platitudes and a bizarre poem full of strange imagery but devoid of much meaning. In the morning, McCool is hung and, true to his word, goes to his death silently. The weather breaks, and the fleet quickly returns to blockading stations in the English Channel.

Ye heavenly powers! Stand by me when I die!
The bee ascends before my rolling eye.
Life still goes on within the heartless town.
Dark forces claim my soul. So strike 'em down.
The sea will rise, the sea will fall. So turn
Full circle. Turn again. And then will burn
The lambent flames while hell will lift its head.
So pray for me while I am numbered with the dead.